The Apple Watch went on sale after the company's quarter ended so we won't get a glimpse of the sales figures just yet. But one analyst told CNBC that high sales expectations for the Apple Watch won't materialize, and could affect earnings and share price laterthis year.

"I look at consensus as being around about 50 million (sales) and the way things are going, I would be looking more like things coming in about 20 million for the first 12 months, best case," Richard Windsor, founder of Radio Free Mobile, said in a TV interview.

"Frankly, I actually think that will be negative for the share price...People are expecting it to have a reasonable impact on the operating line and the cash flow, so I would expect an earnings miss if my 20 million figure turns out to be right."

Estimates 'overdone'

Analyst forecasts for Apple Watch have been wide-ranging. FBR Capital Markets analyst Daniel Ives estimates sales of over 2 million units during the pre-order phase which began on April 10. In a note from last week, he said total shipments of the device could hit 20 million this year. Ming-Chi Kuo, an analyst from KGI however, said the Apple Watch had 631,000 initial shipments. The first of the devices were delivered on Friday. (Tweet this)

Some customers won't be receiving their devices until May or June due to supply constraints, although the Cupertino, CA-based company previously recognized that demand would outstrip supply.

"I don't think it will hit the stock too hard. These estimates are really estimates to be absolute, there is no hard indication as to what actual sales will be," Lawler told CNBC by phone.

The analyst added that revenues from the Apple Watch could make up for the decline in iPad sales, which saw an 18 percent year-on-year drop in the first quarter.

iPhone 'earnings power'

The Street has 14 strong buy, 20 buys, 12 holds and one sell on Apple stock, with an average price target of $141. Despite the hype around Apple's newest device, analysts still agree that the iPhone will really drive earnings.

"We are in the grips of a fairly strong replacement cycle… you're seeing a lot of upgrading from existing Apple products, but also some switching over from Android. And I think that product cycle could run until the end of this quarter," Windsor said.

"So from that point of view this earnings report, while the sentiment is around the Watch, the earnings power is all about the iPhone."